Celestion F12M-150 Triple Cone

So I bought this to use with a FRLR cabinet with my Kemper. A great project which I'm (still) quite proud of. However it's lead to a number of other projects because of how unhappy it has left me with regards to my bass tone. Eventually I've come to the conclusion that the F12M-150 might be the culprit. Most FRFR speakers go down to 52Hz which is still a lot higher than 41 needed for a low E on the bass. This (though clearly stated) has a much higher lower bound at 60Hz. I bought the modeller because, just like many of my dual guitar and bass playing colleagues, then I don't need one cab for bass and one for guitar.

Great for guitar. Useless for bass. Need to build a whole new cab.